title: A Single A1C >= 6.5% Accurately Identifies Type 2 Diabetes/Impaired Glucose Tolerance in African Americans.
abstract: OBJECTIVE
  In 2010, the American Diabetes Association revised its criteria for the diagnosis of diabetes to include A1C ≥ 6.5%; however, this has remained controversial, particularly for African Americans. The objective of this pilot study was to examine the usefulness of a single A1C determination in comparison with a same day 2-hour oral glucose tolerance test to diagnose type 2 diabetes in African Americans.
  
  
  METHODS
  In sum, 195 oral glucose tolerance tests and A1Cs were obtained on the same day from 77 overweight and obese African American women and 6 men over a period of 15 months.
  
  
  RESULTS
  A1C ≥ 6.5% was present in 31 of 195 patients, with 15 of these having type 2 diabetes by oral glucose tolerance test, another 12 having impaired glucose tolerance, and 4 having normal glucose tolerance. This gives a sensitivity of 50% and a specificity of 90%, with a positive predictive value of 48% and a negative predictive value of 91%. A1C ≤ 5.6%, proposed by the American Diabetes Association to indicate normal glucose tolerance, was present in only 28 patients, 10 (35.7%) of whom had normal glucose tolerance, whereas 18 (64.3%) had either impaired glucose tolerance (15 patients) or type 2 diabetes (3 patients). Fasting plasma glucose ≥ 126 mg/dL was present in 5 of 29 patients with type 2 diabetes (sensitivity, 17.2%; specificity, 100%).
  
  
  CONCLUSIONS
  First, A1C ≥ 6.5% was a good "rule in" value to identify impaired glucose tolerance and type 2 diabetes (ie, patients at high risk for micro- and macrovascular complications). Second, A1C ≤ 5.6% did not rule out impaired glucose tolerance or type 2 diabetes. Last, fasting plasma glucose ≥ 126 mg/dL detected less than 1 in 5 cases with type 2 diabetes.
authors.affiliation: Clinical Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania.
authors.forename: Carol J
authors.initials: CJ
authors.lastname: Homko
authors.forename: Linda C
authors.initials: LC
authors.lastname: Zamora
authors.forename: Margaret M
authors.initials: MM
authors.lastname: Kerper
authors.forename: Maria
authors.initials: M
authors.lastname: Mozzoli
authors.forename: Karen
authors.initials: K
authors.lastname: Kresge
authors.forename: Guenther
authors.initials: G
authors.lastname: Boden
keywords: A1C; African Americans; fasting plasma glucose; oral glucose tolerance test